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PACIFIC ROOT CROPS
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4.0 ROOT CROPS IN THE PACIFIC
Tropical root crops are grown widely throughout tropical and subtropical regions
around the world and are a staple food for over 400 million people. Despite a
growing reliance on imported flour and rice products in the Pacific, root crops such
as taro (Colocasia esculenta), giant swamp taro (Cyrtosperma chamissonis), giant
taro (Alocasia macrorhhiza), tannia (Xanthosoma sagittifolium), cassava (Manihot
esculenta), sweet potato (Ipomoea batatas) and yams (Dioscorea spp.) remain
critically important components of many Pacific Island diets, particularly for the
large rural populations that still prevail in many PICTs (Table 4.1).
Colocasia taro, one of the most common and popular root crops in the region, has
become a mainstay of many Pacific Island cultures. Considered a prestige crop,
it is the crop of choice for traditional feasts, gifts and fulfilling social obligations
in many PICTs. Though less widely eaten, yams, giant taro and giant swamp taro
are also culturally and nutritionally important in some PICTs and have played an
important role in the region’s food security. Tannia, cassava and sweet potato are
relatively newcomers to the Pacific region but have rapidly gained traction among
some farmers on account of their comparative ease of establishment and cultivation,
and resilience to pests, disease and drought.
Generations of accumulated traditional knowledge relating to seasonal variations in
rainfall, temperature, winds and pollination, and their influence on crop planting and
harvesting times now lie in jeopardy given the unparalleled speed of environmental
change impacting the region. Left unchecked, climate change will seriously erode food
security and agricultural livelihoods in all Pacific Island countries. To make substantial
reduction in the pending impacts of climate change on agricultural productivity in
the region, climate change must be tackled head on with a calculated and planned
approach that draws on both modern and indigenous agricultural production
practices. Arguably the greatest challenge lies in synthesising and transferring this
knowledge to the many thousands of Pacific Islanders growing crops for the dinner
plate and market place alike. (See TOOLS 1-46 for further information.)
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Table 4.1: Root crop production, populations, total and arable land areas for FAO member
states in the Pacific region
PACIFIC
COUNTRY
Cook Islands
FSM
Fiji
Kiribati
Marshalls
Nauru
Niue
Palau
PNG
Samoa
Solomons
Tonga
Tuvalu
Vanuatu
TARO
CASSAVA *
(tonnes/year) (tonnes/year)
1 500
74 009
2 200
55 773
50
3 300
285 000
18 634
44 000
3 800
145 000
25 000
97 000
Unreported
TOTAL
POPULATION
(year)
19 569 (06)
107 008 (00)
827 900 (07)
92 533 (06)
50 840 (99)
8 800 (07)
1 625 (06)
1 990 (05)
6 600 000 (09)
180 741 (06)
533 672 (06)
101 134 (06)
12 177 (08)
217 000 (05)
RURAL
POPULATION
30%
78%
49%
54%
33%
0%
23%
85%
78%
84%
57%
58%
76%
LAND
AREA
(km2)
236
702
18 272
726
181
21
260
459
462 000
2 831
28 896
747
26
12 189
ARABLE
LAND
12.7%
3.7%
9.2%
2.5%
10.8%
11.6%
2.2%
0.5%
8.8%
0.6%
19.9%
1.7%
*Estimated production source = 2008 FAOSTAT data: www.faostat.fao.org
4 .0 . 1 Root crop n u trition
Root crops are widely available in all PICTs and form one of the main sources of
energy and nutrients for Pacific Islanders. For example, tubers represent almost
40 percent and 50 percent of the energy intake in Tonga and the Solomon Islands,
of which taro is a vital component. The taro tuber (corm) is an excellent source of
both energy and fibre and, when eaten regularly, provides a good source of calcium
and iron. Sweet potatoes and yams are also good sources of energy, which the
body needs to stay active. The yellow and orange varieties of the sweet potato root
contain a high amount of Vitamin A and all varieties contain appreciable quantities
of Vitamin C. Yams provide significant quantities of vitamin B1, vitamin C and
dietary iron and niacin.
Some Pacific root crops such as sweet potato, taro and cassava have leaves that
are also edible and nutritious. Taro leaves, for example, are an excellent source of
protein,dietary fibre and a wide range of vitamins and minerals including carotene,
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potassium, calcium, phosphorous, iron, riboflavin, thiamine, niacin, vitamin A and
vitamin C. (See TOOLS 33 & 44 for further information on nutrition.)
4 .0 . 2 Pacific trade
While Pacific root crops are grown largely for domestic consumption in gardens and
smallholdings, some international trade of root crops is carried out with Australian
and New Zealand and, to a lesser extent, North America. While there is good scope
to expand these and other international trade markets, efforts are also required to
promote and establish intraregional trade of root crops between neighbouring Pacific
Islands. Such trade has the potential to improve regional food security and to create
livelihood opportunities within Pacific Island agricultural sectors.
4 .0 . 3 Storage an d pre se rva tion
Most types of root crops can be “field stored”, meaning left in the ground to grow,
for varying lengths of time until they are needed for eating. The time varies from a
few months to many years in the case of Cytosperma taro. In fact, given that some
root crops, such as Colocasia taro, can perish quite quickly following harvesting,
field storage is often the best solution for keeping root crops fresh.
When field storage is not practicable, there are some traditional methods of
preservation that can be used to extend the shelf life of root crops. One such method
involves storing the tubers underground in purpose-built pits lined with coconut
husks or banana leaves that are then covered with soil. The tubers may be kept for
up 2 to 3 months in this fashion.
It is also possible to bake the tubers in a hot earth oven until an external crust is
formed. The tubers can then be stored for up to a week or more before eating. Or,
they can be preserved by parboiling the root, slicing it thinly and then sun-drying
the tuber slices. Taro root prepared in this fashion will keep up to several months
when stored in a tightly sealed jar, tin or plastic bag.
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In Hawaii and Tahiti, taro is also stored as poi – a food that is commonly consumed
during traditional feasts. Poi is made from Colocasia taro that has been steamed in
an earth oven, peeled and then pounded on a flat stone or a special wooden bowl
(kumete) to form a paste-like texture. During the process of pounding, a small
amount of water is added to achieve the best consistency of the mixture to form the
poi. It can then be eaten fresh, stored overnight to mature (ferment) for flavour, or
stored for several weeks before being consumed.
The spread of freezers through the Pacific region has obviously provided a modern
method of preserving root crops for long-term storage. Peeling and freezing of root
crops can provide convenient storage for several months and is increasingly used by
Pacific agricultural exporters to bypass stringent quarantine requirements imposed
by developed trading partners. (See TOOL 45 for further information on traditional
food storage techniques.)
4 .0 . 4 Growin g con dition s
Because there are a variety of tropical root crops grown in the Pacific, there are
essentially crops suited to almost every climate and growing condition encountered
across the region. Even in locations where the soils are sandy, shallow and nutrient
deficient, as is the case on many low-lying atolls, farmers improve soil growth
conditions through the addition of organic matter and traditional fertilizers.
The variety of soil and rainfall requirements among the different root crops gives
farmers the opportunity to mix-and-match different crops to different growing
conditions. Astute farmers are also able to hedge their bets against variable rainfall
by planting crops with differing soil moisture requirements. For example, cassava,
tannia and sweet potato can be grown in semi-arid regions and are considered more
drought tolerant than yam and taro species. In contrast, most varieties of taro are
best adapted to higher rainfall areas, and some species actually thrive within saturated
soil conditions and even within brackish waters containing 25-50 percent seawater.
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Such conditions would quickly kill most types of root and vegetable crops. Table 4.2
provides an overview of the growth requirements for the major root crops cultivated
in the Pacific region.
4.1 ADAPTATION STEPS FOR ROOT CROPS
In addition to many of the adaptation steps outlined in Modules 2 and 3, it is also
important that farmers do not “store all their eggs in one basket”. Climate change
is likely to be accompanied by increased climate variability that will see increased
frequency and/or intensity of extreme weather events including drought and flooding.
By diversifying root crops and using drought and water tolerant varieties, farmers
can reduce the risk of crop failure and build resilience into their farming practices.
The following three adaptation steps specify root crops but could be applied equally
to other agricultural crops.
~
Step 28 - Growing multiple crops and diversifying crop mixes – to include
drought-resistant varieties of cassava, tannia and taro – provides a useful means
of helping maintain food security during dry spells and periods of mild drought.
It also protects farmers against market fluctuations that may see the demand for
some crops plummet during market surpluses.
~
Step 29 - Awareness among stakeholders of the probable impacts of climate
change on agriculture and root crops is required at all levels. Farmers and relevant
stakeholders should be made aware of the adaptive steps available to maintain
and enhance agricultural production food security in the Pacific region.
~
Step 30 - Monitoring and evaluation systems to determine the success of
agricultural adaptation strategies for root crops are critically important so
that farmers can learn from their mistakes and successes and share this vitally
important information.
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Table 4.2: Description and growth requirements for the major root crops cultivated in the
Pacific region (Primary Sources: See TOOLS 29 & 30.)
ROOT CROP
GENERAL DESCRIPTION AND CROP REQUIREMENTS
TARO
(Colocasia esculenta)
Description: Taro is a perrenial herb that has heart-shaped leaves
and grows 1-2 metres high. It is one of the most widespread root
crops of the humid tropics. Its corm may be harvested 8 to 12
months after planting. The taro corm has limited – approximately
two weeks – storage life post harvest. While there are eight
recognized variants of common taro, only two are usually
cultivated. Most of the taro grown in the Pacific is Colocasia
esculenta (L.) Schott var. esculenta (also known as “dasheen”
taro) which has a large central corm. Colocasia esculenta (L.)
Schott var. antiquorum is often preferred in places where taro
Known as:
~ dalo in Fiji,
~ talo in Samoa and Tonga,
~ te taororo in Kiribati,
~ taro tru in PNG,
~ aelan taro in Vanuatu.
is grown primarily for leaves because it has a central corm with
several relatively large “cormels” surrounding it. Colocasia taro is
susceptible to some pests and diseases including taro leaf blight,
plant leaf hoppers, caterpillars and mites.
Crop requirements: Taro generally grows best in a wet, humid
environment. Most varieties do not tolerate drought. It is
typically grown in “wetland” conditions in upland areas with
rainfall over 2 000mm/year but can tolerate lower rainfall if it
is well distributed throughout the growing season. It responds
well to N, P & K applications and is often the first crop grown
in rotation following bush clearing. It is sometimes grown as
a monocrop but is also widely planted in multiple cropping
systems with other root crops including bananas, plantains and
tree crops. It is not tolerant to salinity and, while shading may
improve establishment, production is higher when exposed
to direct sunlight in later stages of growth. It can be grown
in both light (sandy) or heavy (clay) soils but prefers slightly
acidic growing conditions (pH 5.5-6.5) and does not compete
well with weeds during establishment.
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Building resilience to climate change - root crop and fishery production
ROOT CROP
GENERAL DESCRIPTION AND CROP REQUIREMENTS
GIANT SWAMP TARO
(Cyrtosperma Chamissonis)
Description: Giant swamp taro is a “lowland” taro species
and the largest of the taro family. It may reach heights of
4-5 metres, with leaves and roots much larger than Colocasia
taro. It is one of the few subsistence crops that grows well on
atolls and within swampy areas of other islands, and its corm
can reach weights of 80 kg or more! It may be field stored in
the ground for very long periods – up to 30 years or more – and
accordingly has traditionally been an important emergency crop
in times of natural disaster and food scarcity. It is relatively
resistant to disease and pests but is susceptible to taro beetle.
It can take several years to mature but is commonly left for 15
years or more before harvest.
Known as
~ puraka in Cook Islands,
~ te babai in Kiribati,
~ pula’a in Samoa,
~ via kan in Fiji,
~ pulaka in Tokelau, Tuvalu,
~ simiden in Chuuk,
~ swam taro in PNG,
~ navia in Vanuatu.
Crop requirements: As indicated by its name, giant swamp
taro has adapted to growth within fresh water and coastal
swamps. It is also commonly grown in purpose-built swamp
pits in low-lying coral atolls. In the case of constructed pits
various kinds of organic matter and fertilizer are usually added
to the pit to improve the soil fertility, physical properties and
waterholding capacity. Giant swamp taro is not suitable for
growing in upland or rainfed conditions. It exhibits some shade
tolerance and is considered mildly tolerant of saline growing
conditions compared to other taro species, and can be grown
in mildly brackish water.
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PACIFIC FOOD SECURITY TOOLKIT
Building resilience to climate change - root crop and fishery production
ROOT CROP
GENERAL DESCRIPTION AND CROP REQUIREMENTS
GIANT TARO
(Alocasia macrorrhiza)
Description: Giant taro is a hardy plant with a thick starchy
edible stem. It is predominantly found in Tonga and Samoa and
is not as popular as other types of root crops. The corm may
grow up to 30 cm or more in diameter and up to 2 metres in
length. It is increasingly used as fodder for animals in some
PICTs but will be eaten when other foods are in short supply.
It is a hardy crop that is resistant to insect and pests but often
sought out by foraging pigs. It can be harvested after 12 to
18 months but can be left to grow in place for several years,
Known as:
~ ta’amu in Samoa, Tuvalu,
~ kape in Cook Islands, Tonga,
~ te kabe in Kiribati,
~ paragum in PNG,
~ fila in Solomon Islands,
~ via in Fiji,
~ pia in Vanuatu.
making it an important crop in times of food scarcity.
Crop requirements: This is an upland crop that grows best in
well-drained soils with well-distributed rainfall of more than
2 000 mm/year. The crop does not tolerate poor drainage but
may be relatively resistant to water stress and shade as it is
often grown in stony or rocky soils and within multiple cropping
systems with taller crops. It is not considered salt tolerant but
is suited to both light (sandy) soils or heavier soils found on
volcanic islands.
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Building resilience to climate change - root crop and fishery production
ROOT CROP
GENERAL DESCRIPTION AND CROP REQUIREMENTS
TANNIA
(Xanthosoma sagittifolium)
Description: This crop is considered easy to grow and produces
a relatively high yield within 6 to 12 months after planting. It
is often grown in Melanesia, where both its pointed leaves and
roots are eaten, but is not particularly suited to sandy, infertile
atoll soils. Tannia was brought to the Pacific about 100 years
ago and is resistant to many of the pests and diseases that affect
Colocasia taro. It is also much more tolerant of drought than
common taro with the added advantage that, once harvested,
the root may be stored in a cool, dry place for several months.
Known as:
~ dryland taro or talo futuna in Tonga,
~ tarua in Cook Islands,
~ talo palagi in Samoa,
~ taro Fiji in Vanuatu,
~ singapo or taro kongkong in PNG,
~ te tannia in Kiribati.
Crop requirements: This crop is considered an upland taro
species and grows best in areas receiving between 1 500 to
2 000 mm of rainfall per year, although it can be grown in
areas with rainfall as low as 1 000 mm/year. The plant roots
within 15-20 cm of the soil surface and requires well-drained
and relatively fertile growing conditions. It is not well suited
to planting on sandy, nutrient-deficient atoll soils but can be
grown where these soils have been amended with organic
materials. It is not considered salt tolerant.
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Building resilience to climate change - root crop and fishery production
ROOT CROP
GENERAL DESCRIPTION AND CROP REQUIREMENTS
CASSAVA
(Manihot esculenta)
Description: The cassava plant is a relatively new import to the
Pacific and, given that it is easy to grow and simple to prepare,
is becoming increasingly popular as a food and livestock
fodder crop. Its nutritious leaves are eaten in some areas. Its
starch-rich root is used in industry elsewhere in the world for
glue-making and other industrial purposes.
Known as:
~ maniota in Cook Islands,
~ tapioca or tavioka in Fiji,
~ manioka in Samoa,
~ manioc in Vanuatu
Crop requirements: Grows best in well-distributed rainfall
setting of 1 000-1 500 mm/year. Higher rainfall levels can reduce
tuber growth. It is considered highly tolerant of drought and can
be grown in areas receiving as low as 500 mm/year. Cassava
has low nutrient requirements and can be grown in relatively
infertile soils. Hence it is often used as a final crop in rotations
prior to returning land to fallow. It competes well with weeds
but is sensitive to shade.
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Building resilience to climate change - root crop and fishery production
ROOT CROP
GENERAL DESCRIPTION AND CROP REQUIREMENTS
SWEET POTATO
(Ipomoea batatas)
Description: Sweet potato is a creeping plant and the only
economically important species of the family Convolvulaceae.
The starchy, tuberous roots are the major source of food, but
the leaves are also a useful source of vegetable greens in
some countries.
Know as:
~ kumara in Cook Islands
~ umala in Samoa,
~ kumala in Fiji, Tonga,
~ kaukau in PNG,
~ te kaina in Kiribati
In PNG, it is the major crop and staple food. It is also an
important crop in the Solomon Islands and Tonga, and is
increasingly found in other PICTs.
Crop requirements: Grows best in high rainfall areas of about
1 500-2 500 mm/year. Higher rainfall may induce excessive
vegetative growth at the expense of tuber growth. Grows well in a
variety of well-drained soil types but does not tolerate shading.
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Building resilience to climate change - root crop and fishery production
ROOT CROP
GENERAL DESCRIPTION AND CROP REQUIREMENTS
YAMS
(Dioscorea alata, D. esculenta,
D.bulbifera, D.pentaphylla,
D.hispida, D.rotundata, and
D.trifida, D. nummularia)
Description: Yams are a high value food that are easily grown
and mature quickly in the right soil conditions. Unlike most
other tropical root crops, yams exhibit good keeping qualities
and may be harvested well in advance of eating.
Known as:
~ u’i in Cook Islands,
~ ufi in Samoa,
~ uvi in Fiji,
~ yam/mami in PNG.
Crop requirements: Most varieties of yams grow best in
rainfall of >1 500 mm/year and require a minimum 6-month
growing season with well-distributed rainfall. Yams do not
tolerate poorly drained soils or waterlogging. They are mildly
drought tolerant but do not compete well with weeds for soil
nutrients. Yams should be staked to improve yield, and reduce
weed competition and the incidence of anthracnose disease.
They exhibit early shade tolerance during establishment but
require full sun for good yields.
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